1. Field of the Invention
The present invention relates to communication methods, communication apparatuses, software programs and computer-readable recording media, and more particularly to a communication method and communication apparatus that monitor line quality during communication and re-set communication parameters such as a communication rate and a modulation method according to need so as to ensure a stable communication state, and to a software program for causing a computer to carry out such communication, and to a computer-readable recording medium that stores such a software program.
2. Description of the Related Art
FIG. 1 shows a state where a terminal unit 10 on a user's side such as a personal computer is connected to a server 20 at an access point of an Internet service provider or the like via a communication line 30 such as a telephone line. The terminal unit 10 connectable to the communication line 30 as mentioned above is provided with a communication device that establishes connection to the communication line 30, that is, a modem 11. In order to ensure the stable communication state, the modem has functions of constantly monitoring the communication state and re-setting (, newly setting or updating) various communication parameters if necessary, such as a speed of circuit, communication protocol, error correction method and data compression method.
According to the functions, normal communication is temporarily suspended and a communication parameter re-set operation (hereinafter referred to as a “re-set operation”) as described above is activated when, as a result of a monitoring operation as mentioned above, it is detected that an input signal level, a S/N ratio (signal-to-noise ratio) and the like drop to equal to or less than predetermined levels due to noise or the like on the communication line 30. In other words, the operation of sequentially re-setting (, newly setting or updating) the various communication parameters is performed while negotiation between the modem 11 and a modem 21 of the server 20 is performed via the communication line 30. In addition, as for noise, there are power noise, electromagnetic noise by a microwave and the like, and noise specific to an inverter of an air conditioner, for example.
FIG. 2 is a function block diagram of the modem 11. As shown in FIG. 2, the modem 11 includes a controller 11a, a modulator/demodulator 11b and a line interface part 11c. The controller 11a transmits/receives a signal to/from a personal computer (PC) 12. The line interface part 11c is connected to the communication line 30 such as a telephone line and the like. The modulator/demodulator 11b is provided between the controller 11a and the line interface part 11c. The modulator/demodulator 11b has a function of converting the signal from the personal computer 12 to a signal for communication by compression and modulation. Additionally, the modulator/demodulator 11b has a function to convert the signal for communication received at the line interface part 11c to a signal that can be used in the personal computer 12 by demodulation and decompression.
Further, generally, the functions of the controller 11a and modulator/demodulator 11b of the modem of today are realized by software, since the operation of a CPU in a computer is speeding up, for example. In this case, such software is called driver software. The driver software functions on the Operating System (OS) of a personal computer and carries out the modem functions as described above.
In the system shown in FIG. 1, the Internet service provider performs a user authentication operation (hereinafter referred to as a “authentication operation”) in the beginning of the communication with a user, when providing, to the user, service according to the contract previously made with the user. In the authentication operation, the user is identified and authenticated by being prompted to input such as a user name and a user ID that are set when concluding the contract. After the identification and authentication of the user, the Internet service provider (hereinafter simply referred to as an “ISP”) connects the terminal unit 10 of the user to a communication network such as the Internet. The user can enjoy various services provided via the Internet only when the connection is established by the ISP after the authentication operation.
FIG. 3 is a flow chart showing the operation in the above-described case. In step S1, a line connection operation by the modem 11 is started by a dial-up operation of application software (hereinafter simply referred to as an “application”) in the personal computer 12 as the terminal unit 10 on the user's side. Then, the modem 11 transmits a line connection request to the modem 21 provided to the server 20 at the access point of the ISP. As a result, in step S2, the negotiation between the modems 11 and 21 is performed. In step S3, whether or not the negotiation succeeds is determined. When the various communication parameters are set and the negotiation ends in success (YES in step S3), the connection of the communication line 30 is completed in step S5.
When the setting of the communication parameters by the negotiation ends in failure (NO in step S3), the communication line 30 is disconnected in step S4, and the process is returned to the application again. Thereafter, steps S1 through S3 are repeated until the re-setting (, new setting or updating) of the communication parameters succeeds when the user gives a restart instruction.
When the connection of the communication line 30 is completed in step S5, the process is handled by the application on the server 20 of the ISP from step S6. In step S6, the confirmation of the ID and a password is performed as the authentication operation. In step S7, whether or not the confirmation succeeds is determined. When the confirmation succeeds (YES in step S7), the ISP connects the communication line 30 to a network in step S8. Consequently, in step S9, the user can enjoy the service via the network by Net-surfing and the like.
However, when the re-setting operation is activated during the authentication operation in step S6 due to noise or the like, the normal communication is stopped for performing the negotiation between the modems 11 and 21. Accordingly, the authentication operation is aborted. As a result, the decision result in step S7 is NO, and the process returns to the application on the user's side. When the user gives an instruction of restarting the connection with the communication line 30, the communication line connection operation starting from step S1 is started.
FIGS. 4 and 5 show the operation flow that organizes the above-described operation and further includes the function of a authentication timer. First, FIG. 4 shows a case where the authentication succeeds without being aborted by the disconnection of the communication line 30 due to noise and the like. In this case, after a line connection operation (step S21) and the completion of the line connection (step S22), the authentication operation (step S23) is started. At this moment, the authentication timer is activated in step S24. Then when the authentication operation is correctly carried out and ends in step S25, in step S26, the communication line 30 is connected to the network and the user can enjoy Net-surfing with the user terminal 10. In this case, the authentication timer is cleared in step S26, by the completion of the authentication operation in step S25.
Next, by referring to FIG. 5, a description will be given of a case where the authentication operation is aborted by the disconnection of the communication line 30 due to noise, and as a result, the authentication ends in failure. In this case, the operations from step S21 to step S23 are the same as those corresponding steps in FIG. 4. However, in FIG. 5, when the communication state is worsened due to noise and the like in step S31, the re-set operation is performed in step S34 so as to recover the communication state. In this case, in order to perform the negotiation between the modems 11 and 21, the normal communication is suspended in step S32. Consequently, the authentication operation cannot be continued and is aborted in step S33.
Then, as a result of the re-set operation in step S34, the re-setting of the communication parameters is completed, the communication for the authentication operation is restarted, and the authentication operation is restarted. However, in this case, since the authentication operation is aborted in step S33, due to the passage of time, there is a case where the authentication timer times out before the authentication operation succeeds (step S35). In this case, the authentication operation ends in failure (“failure in authentication”), and in step S36, the application on the server 20's side disconnects the communication line 30 via the modem 21. Thus, it is necessary for the user to reattempt from step S21, that is, the connection operation of the communication line 30.
For example, in a case where, since the state of the communication line 30 is wrong, due to noise and the like (step S31), the “failure in authentication” because of the time out of the authentication timer (step S35) and the disconnection of the communication line 30 (step S36) caused by the “failure in authentication” is repeated more than once, the user cannot, for an indefinite period, enjoy the service via the network which service is a desired object.
Next, referring to FIG. 6, a more detailed description will be given of the cause of the above-described situation. As shown in FIG. 6, when the line connection is completed in step S41 (corresponding to step S5 in FIG. 3, or in step S22 in FIGS. 4 and 5), in step S42, the modem 11 on the user's side starts data transmission/reception with the modem 21 of the server 20 to which modem the communication line 30 is connected in step S41. Accordingly, in step S61, the application of the server 20 transmits a request for the ID and password as the authentication operation. In response, in step S62, the application on the user's side transmits the ID and password according to the input by the user.
On the other hand, while the communication line 30 is connected (step S43), when the communication state is temporarily degraded due to noise or the like in step S44, if a communication line monitor function is ON (YES in step S45), the modem 11 detects the communication state. Further, if a re-set function is activated and effective (YES in step S46), in step S47, the modem 11 suspends the general communication (data transmission/reception) for the re-set operation. It should be noted that, in step S45, it is determined whether or not the communication line monitor function is ON. In addition, whether or not the re-set function is ON is determined in step S46. Consequently, the authentication operation cannot be continued. Then, in step S48, the modem 11 performs the re-set operation of the communication parameters. As a result, the data transmission/reception is restarted in step S49, and the communication line 30 assumes a connected state in step S50. Accordingly, the authentication operation is restarted. When the authentication succeeds (YES in step S64), the communication line 30 is connected to the network. However, when the authentication timer times out due to the delay in confirmation of the ID and password (step S63) by the suspension of the authentication operation, the authentication ends in failure (NO in step S64), and the communication line 30 itself is disconnected by the modem 21 of the ISP in step S66.